"I don't think it's understood very well.
"If you hurt your knee you'd go to the physio but people don't treat their minds the same way," Kirwan said.
"There is a high suicide rate in our rural areas and it's tough times for farmers at the moment. I don't pretend to relate to how hard it is because I'm a city boy but I think when your tough times turn into mental illness you need to reach out and get help.
"There is a trend that people in the rural areas don't do that."
He spoke about his lowest points as an All Black.
"What do I have to be depressed about?" he would ask himself.
He was living his dream but was dead inside.
"Mental illness took the joy out of my life. Everything I loved."
Kirwan said his way out was through seeking help and taking pleasure in everyday activities.
"I started to enjoy the little things, wellness is everyday and it's about balance."
Simple things such as reading and cooking helped him through some dark times.
"I would start to feel the water in the shower and really taste my morning coffee."
Kirwan had the audience fully engaged and even got them on their feet dancing and hugging.
Westpac has partnered with Kirwan to help him share his message and open up dialogue about mental health and well-being.
Last month he toured the South Island to speak at rural community halls and schools.
He will speak to Lindisfarne College and Hastings Girls' students today.